Berlin 2008 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 29: Poster II

DY 29.66: Poster

Donnerstag, 28. Februar 2008, 16:00–18:00, Poster C

Vibrational excitations in systems with correlated disorder — •Walter Schirmacher¹, Bernhard Schmid², Constantin Tomaras¹, Gabriele Viliani³, Giacomo Baldi⁴, Giancarlo Ruocco⁵, and Tullio Scopigno⁵ — ¹Phys.-Dept. E13, TU München — ²FB Physik. Uni Mainz — ³Dipt. di Fisica, Univ. di Trento, Italy — ⁴INFM-CNR CRS-SOFT OGG c/o ESRF, Grenoble, France — ⁵Dipt. di Fisica, Univ. di Roma; CRS SOFT-INFM-CNR c/o Univ. di Roma, Italy

We investigate a d-dimensional model (d = 2,3) for sound waves in a disordered environment, in which the local fluctuations of the elastic modulus are spatially correlated with a certain correlation length. The model is solved analytically by means of a field-theoretical effective-medium theory (self-consistent Born approximation[1]) and numerically on a square lattice. As in the uncorrelated case [1,2] the theory predicts an enhancement of the density of states over Debye’s ω^d−1 law (“boson peak”) as a result of disorder. This anomaly becomes reinforced for increasing correlation length ξ. The theory predicts that ξ times the width of the Brillouin line should be a universal function of ξ times the wavenumber. Such a scaling is found in the 2d simulation data, so that they can be represented in a universal plot. In the low-wavenumber regime, where the lattice structure is irrelevant, there is excellent agreement between theory and the simulation [3].

[1] W. Schirmacher, Europhys. Lett. 73, 892 (2006)

[2] W. Schirmacher et al. Phys. Rev. Lett. 98, 025501 (2007)

[3] W. Schirmacher et al. cond-mat 0711.1329